Prof. Allen Guelzo wrote a July 1 article on the Battle of Gettysburg for the New York Times' Disunion blog.

From Disunion:

It took no more than a few days after the Battle of Gettysburg for the men who had fought there to realize how important it had been. “The Battle of Gettysburg, like Waterloo, must stand conspicuous in the history of all ages,” wrote a staff officer, Frank Aretas Haskell, who himself would die less than a year later in a much less conspicuous battle at a place called Cold Harbor. And even by the most remote measure, Haskell was right.

For over a year before, the Confederate general Robert E. Lee and his homespun Army of Northern Virginia had defied every expectation, and routinely humiliated every thrust its opposite number, the Army of the Potomac, had made at the Confederacy’s vitals in Virginia. Union generals – George McClellan, Ambrose Burnside, Joe Hooker – had been installed, and just as readily removed, until by 1863, a soldier in the 16th North Carolina could boast that they were merely waiting for the Yankees “to put up another General for us to whip.” When instead it was the Confederates who were defeated at Gettysburg, the surprise was almost unbearable. “The campaign is a failure,” wrote one rebel officer to his sister on July 17, “and the worst failure that the South has ever made … and no blow since the fall of New Orleans has been so telling against us.”